Devices that receive radio frequency (RF) signals often employ a down-conversion mixer or detector circuit to produce a signal at a lower frequency range. This signal may be at an intermediate frequency (IF), or at baseband when direct conversion techniques are employed.
To increase its alternating current (AC) level, a detected signal may be sent to an amplifier. Additionally, one or more filters (e.g., low pass or band pass filters) are conventionally placed between the output of the mixer or detector and the input of the amplifier. Such filters may separate relatively low-frequency modulation components in the signal from residual RF components, and limit the signal processing bandwidth to reduce noise.
Conventional filter and amplifier arrangements typically block or degrade direct current (DC) signal components that are provided by the detection circuit. For example, certain conventional arrangements incorporate high pass filters to block the DC offsets that are byproducts of a homodyne detector configuration.
Such blocking of DC signal components can lead to several disadvantages. These disadvantages may include a loss of static phase information, a loss of loop stability, an impairment of system transient response, as well as a degradation of other system parameters.